The haplodiploid sex-determination system of ants gives rise to conflict between queens and workers over colony sex ratios, and the female-biased allocation ratios seen in many species suggest that workers often prevail in this conflict. We exchanged queens between male- and female-specialist colonies of the fire ant Solenopsis invicta. These exchanges quickly reversed the sex-ratio biases of a...

Sex allocation theory predicts that reproducing individuals will increase their fitness by facultatively adjusting their relative investment towards the rarer sex in response to population shifts in operational sex ratio (OSR). The evolution of facultative manipulation of sex ratio depends on the ability of the parents to track the conditions favouring skewed sex allocation and on the mechanism...

The Drosophila snf gene is a positive regulator of the sex determination gene Sex-lethal in both the germline and the soma. Its role in the soma is only evident when the probability of Sex-lethal activation has been reduced. For instance, in an otherwise wild-type background, females homozygous for a weak snf mutation produce both male and female progeny; however, when mated to males hemizygous...

Sexual arousal is category-specific in men; heterosexual men are more aroused by female than by male sexual stimuli, whereas homosexual men show the opposite pattern. There is reason to believe that female sexual arousal is organized differently. We assessed genital and subjective sexual arousal to male and female sexual stimuli in women, men, and postoperative male-to-female transsexuals. In c...

All insects in the order Hymenoptera have haplodiploid sex determination, in which males emerge from haploid unfertilized eggs and females are diploid. Sex determination in the honeybee Apis mellifera is controlled by the complementary sex determination (csd) locus, but the mechanisms controlling sex determination in other Hymenoptera without csd are unknown. We identified the sex-determination...

BACKGROUND Transgender women are a key risk group for HIV, and epidemiologic studies have attributed high rates of HIV infection to behaviors associated with sex work in this population. This systematic review compared HIV prevalence among transgender female sex workers (TFSWs) with prevalence among transgender women who do not engage in sex work, male sex workers, and biologically female sex w...

It is difficult to develop good arguments when the central terms of discussion are unclear – as with current confused state sex and gender terminology. Sports organisations sports researchers often talk in they mean sex; or use vocabularies interchangeably. We propose terminology that distinguishes from gender. Historically, sport has been based on sex, seen various verification procedures spec...

Many studies have used visual adaptation to investigate how recent experience with faces influences perception. While faces similar to those seen during adaptation phases are typically perceived as more 'normal' after adaptation, it is possible to induce aftereffects in one direction for one category (e.g. female) and simultaneously induce aftereffects in the opposite direction for another cate...

This study was performed to clarify the sexual orientation in a 19-year-old homosexual male and a 20-year-old homosexual female by using a functional magnetic resonance imaging (fMRI) with viewing male and female erotic nude pictures. The sex hormone levels of the homosexual male and female were in the normal range of healthy heterosexual males and females, respectively. In both homosexuals mor...